2018年2月22・23日に、愛媛大学において、桂智男教授(BGI, University of Bayreuth)による国際フロンティアレクチャーを、23日には国際フロンティアセミナーを開催しました。研究員等5名、学生5名が参加し、電気伝導度とマントル鉱物の物性などについてお話し頂きました。
＜学生の声＞
I was very happy to enjoy the two days “Core-Mantle Coevolution” International Frontier Seminar given by one of the state-of-the-art high pressure earth scientists Prof. Katsura from BGI. We not only systematically learned the basic knowledge about physical and chemical properties of mantle materials from many aspects, such as electrical conductivity, viscosity and thermal dynamics of the Earth’s interior, but also the latest progress on above issues. He was ready to help us and patiently explain our every questions during the lecture. We really cherished this wonderful lecture, which will lay a solid foundation for our further study. (Chaowen Xu)
GRC & MEXT Shin-Gakujutsu “Core-Mantle Coevolution” International Frontier Lecture
| 日時 | 2018年2月22（木）-23日（金）9：00 – 16:00 |
| 場所 | 愛媛大学総合研究棟Ｉ会議室#486 |
| 講師 | Prof. Tomo Katsura (BGI, University of Bayreuth) |
| 題目 | Physics and Chemistry of the Earth’s mantle |
| 要旨 |
Basic understanding of physical and chemical properties of mantle materials is essential for investigating the structure and dynamics of the Earth’s mantle. In this lecture, we will discuss the following three topics from various background knowledges necessary for study of the Earth’s interior. Part 1: Thermochemistry of binary solutions The major mantle minerals such as olivine, pyroxenes, wadsleyite, ringwoodite, garnet (majorite), bridgmanite, ferropericlase and post-perovskite are ferromagnesian minerals. Therefore, binary chemical equilibrium is vital to understand the structure of the mantle. In this lecture, we will discuss thermochemistry from its basis to equilibrium of non-ideal solutions. Part 2: Equation of state Density is an essential parameter to investigate the structure and dynamics of the Earth’s interior. To describe change in density as a function of pressure and temperature, various kinds of equation of states were proposed. In this lecture, we will discuss equation of states frequently used in geophysics for investigation of the Earth’s mantle. Part 3: Electrical conductivity Electrical conductivity is a physical parameter of the Earth’s interior that can be remotely estimated from the Earth’s surface. We will discuss electrical conduction mechanism in upper-mantle minerals, and attempt to explain geophysical observation on conductivity structures of the oceanic asthenosphere |
| 問い合わせ | A04-1 土屋卓久 |
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The 69th GRC & The 14th MEXT Shin-Gakujutsu “Core-Mantle Coevolution” International Frontier Seminar
| 日時 | 2018年2月23日（金）16:30 – 18:00 |
| 場所 | 愛媛大学総合研究棟Ｉ会議室#486 |
| 講師 | Prof. Tomo Katsura (BGI, University of Bayreuth) |
| 題目 | Binary phase relations between ringwoodite and bridgmanite + ferropericlase: implication for sharpness of the 660-km discontinuity |
| 要旨 |
Short wave-length seismic reflections from the 660 km discontinuity indicate that the 660-km discontinuity is extreme sharp, namely less than 2 km thick. Since the Earth’s mantle is considered to consist of ferromagnesian silicates, and the 660-km discontinuity is usually attributed to dissociation of ringwoodite to bridgmanite + ferropericlase, the extreme sharpness of the 660-km discontinuity must be explained by the pressure interval of the ringwoodite + bridgmanite + ferropericlase three-phase regions. However, the thickness less than 2 km corresponds to a pressure interval less than 0.1 GPa. Such a small pressure interval was, however, too difficult to investigate by means of high-pressure experiments. In this study, we have determined the binary loop of ringwoodite + bridgmanite + ferropericlase at a temperature of 1700 K. More concretely, we simultaneously determined transition pressures at Mg2SiO4 and (Mg0.7Fe0.3)2SiO4 compositions by means of in situ X-ray diffraction in a multi-anvil press to estimate pressure difference between the Mg end-member transition and the ringwoodite – bridgmanite – ferropericlase – stishovite four-phase coexistence. Then, we estimated compositional width of the binary loop by means of thermochemical calculation using data available in literature. The striking difference from previous investigations is that the four-phase coexistence is located at higher pressure than the Mg end-member transition at 1700 K. The pressure difference was found to be 0.14 ± 0.11 GPa. The compositional difference between ringwoodite and bridgmanite + ferropericlase satisfying the observation by in situ X-ray diffraction is 1 mol% at this temperature. this difference becomes smaller with temperature, and virtually zero at temperatures of 2000 to 2300 K. From these investigations, we have concluded that the thickness of the ringwoodite + bridgmanite + ferropericlase binary loop is essentially zero at mantle temperatures, which explains the sharpness of the 660-km discontinuity |
| 問い合わせ | A04-1 土屋卓久 |
